The chitinase 3-like 1 (CHI3L1) gene, a cellular survival factor against several environmental and psychosocial stresses, has been sown to be more highly expressed in the hippocampus and prefrontal cortex of patients with schizophrenia than unaffected individuals. We recently reported a significant association between schizophrenia and SNP rs4950928, which is located in the promoter region of the CHI3L1 gene, in a Japanese population. The G-allele at this SNP in the gene has been associated with higher transcriptional activity in a luciferase reporter assay and with higher mRNA levels in the peripheral blood cells of patients with schizophrenia. We investigated the impact of the CHI3L1 polymorphism rs4950928 on serum YKL-40 levels, the protein product of CHI3L1. We found that individuals with the G-allele, who were more prevalent among patients with schizophrenia, had significantly higher serum YKL-40 levels (p=0.043). Personality traits are considered to be an important aspect of schizophrenia primarily because they may influence symptoms and social functioning. Personality trait analyses using the temperament and character inventory (TCI) indicated that schizophrenic patients have a unique personality profile that appears to be present across cultures. We hypothesized that higher serum YKL-40 levels are associated with personality trait in patients with schizophrenia. Thus, we next examined the impact of the risk CHI3L1 polymorphism on personality traits using the TCI. We found that individuals with the G-allele had significantly higher self-transcendence scores (p=0.0054). These findings suggest possible associations between the SNP in the CHI3L1 gene, the risk for schizophrenia, and higher serum YKL-40 levels and personality traits in a Japanese population.
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